1. Field of the Invention
The present invention relates to a voltage control circuit for a semiconductor apparatus such as an integrated circuit (referred to as an IC hereinafter), a large scale integrated circuit, and more particularly, to a voltage control circuit for a semiconductor apparatus capable of controlling an output voltage to be applied to a load circuit thereof.
2. Description of the Related Art
FIG. 1 is a circuit diagram showing a voltage control circuit 10 of a conventional IC.
Referring to FIG. 1, the conventional IC comprises the voltage control circuit 10, and a load circuit 3 for performing a predetermined operation, which are mounted in a package of the conventional IC. The voltage control circuit 10 comprises a reference voltage generator 1, an error amplifier 2 comprising four metal oxide semiconductor field effect transistors T2 to T5, and a control transistor T1 of a metal oxide semiconductor field effect transistor. The metal oxide semiconductor field effect transistor is referred to as a MOSFET hereinafter. In the conventional IC, an external voltage source +Vcc for outputting a predetermined direct-current source voltage is electrically connected through the control transistor T1 to the load circuit 3.
The reference voltage generator 1 comprises two resistors R1 and R2 for dividing the source voltage outputted from the external voltage source +Vcc into a predetermined direct-current reference voltage with a dividing voltage ratio of R2/(R1+R2), and applying the divided reference voltage to the error amplifier 2. The error amplifier 2 compares an output voltage to be applied from the external voltage source +Vcc through the control transistor T1 to the load circuit 3, with the reference voltage outputted from the reference voltage generator 1, and drives the control transistor T1 according to the comparison result thereof.
In the conventional IC as described above, even though there is a large change in a load current flowing from the voltage source +Vcc to the load circuit 3, the load circuit 3 can receive a predetermined stable voltage from the voltage source +Vcc through the voltage control circuit 10 since the output voltage is controlled so as to keep a predetermined constant voltage.
However, in the conventional voltage control circuit, even though it is not necessary to supply a large current to the load circuit 3, an unnecessary current always flows in the error amplifier 2 and the reference voltage generator 1.
As a result, when the conventional voltage control circuit 10 of this type is provided in an IC of an electronic apparatus to which electric power is supplied from a battery such as a portable electronic apparatus, there is such a problem that the life of the battery becomes shortened since the above-mentioned unnecessary current flows therein even though the load circuit 3 which is an internal circuit of the IC does not require a relatively large current.